This application is to continue our long-standing research in the evolving risk factors and outcomes of bronchopulmonary dysplasia (BPD) and other neonatal conditions of very low birth weight (VLBW, < 1500g) infants and children. It is proposed to comprehensively document the neonatal and early childhood course and outcomes of all VLBW births in Wisconsin occurring during the calendar years 2003 and 2004 (800-850 per year), using established methodology with added risk factor information to examine currently proposed inflammatory hypotheses of BPD etiology. The research will also implement and validate new diagnostic criteria for the severity of BPD developed by a recent NIH workshop. Comprehensive follow-up of all children to age 2, and those born in 2003 to impulse oscillometry (lOS) testing at age 4 years, will generate regional data on NICU outcomes in an era when extremely small neonates survive. lOS is a sensitive method that is especially appropriate for use in children to measure the function of the airways. The research is important to clinical practice as it will: (1) provide a comprehensive picture of the outcomes of unselected VLBW infants born in the present era of care, (2) examine a readily available marker for the inflammatory process hypothesized to evolve into BPD and other complications, (3) identify high risk sub-groups for future interventions, and (4) generate hypotheses regarding clinical practice to be tested by randomized trials.